I want to try and achieve a better black level with my Z4. I project onto a white wall at 56" wide with a throw distance of 100". My room is light controlled via black out blinds leaving just a very small amount of ambient light. I cannot try a screen at this time or project any bigger so I'm thinking that some kind of neutral density filter might help me achieve blacker black's. Any tips on what to go for and where I might find them would be most appreciated.